1. Field of the Invention
This invention is in the field of measuring the concentration of electrolyte solutions, such as sodium hydroxide. In particular, it relates to a device for measuring the change in power or voltage which is proportional to the concentration of the solution.
2. Description of the Prior Art
It is highly desirable to have a concentration measuring device which is efficient and accurate for large ranges of concentrations. Chemical analysis is a relatively long procedure and is not a practical solution to a large number of concentration measurements. It is particularly not applicable to a situation where fluid in a system is continuously monitored.
Previous systems such as U.S. Pat. No. 3,358,223 to Birnstingl proposed an electronic concentration meter to monitor the concentration of a solution. While there are advantages in the system disclosed, it has a serious disadvantage. Because the Birnstingl device directly measures conductivity, it has a limited range through which it can operate. Concentration levels over about 10 percent cause serious inaccuracies in the outputs of this type of concentration meter.
This invention provides an efficient and accurate system for determining the concentration of a solution. It is an electronic system which may be utilized to determine concentration quickly but does not have the disadvantage of being inaccurate over a certain level of concentration. This invention, instead of measuring the conductivity of the solution per se, measures the power absorption of the solution which is proportional to the concentration of the solution. Since voltage is directly related to power, both terms are used herein to refer to the absorption characteristic of the solutions.
By utilizing a constant temperature device, a linear relationship is obtained between the power absorbed by a solution and the percent of caustic in solution. Thus, accurate results can be obtained.
Alternately, a family of curves can be used to determine the concentrations if the temperature is not controlled.